A. Technical Field
This invention relates generally to skew identification and notification, and more particularly to the detection and notification of a skewed channel within a parallel connection in an electrical system.
B. Background of the Invention
Data traffic is oftentimes communicated on multiple parallel channels to a terminating node or component. This multi-channel communication may be implemented in a network system in which a signal is transported through a network on a multiple channels to a receiving node. Multi-channel communication may also be implemented within a node or within an integrated chip in the node. Certain components, such as demultiplexers and deserializers, within electrical circuitry are used to convert a serial stream of data into parallel data channels. In particular, these components separate or divide a serial signal onto multiple parallel channels that are output from the particular component. This demultiplexing and/or deserializing function within electrical circuitry provides a more effective method for communicating and processing high data rate signals within an electrical system, node or integrated circuit.
The maintenance of timing between these parallel channels is important in the operation of the circuitry. Proper operation of components within the path of the signal may rely on the timing of these channels falling within a certain skew error margin. In particular, certain components may require that the skew on each of the parallel channels fall below an acceptable threshold so that the signal may be properly processed, communicated or reconstructed.
Standards and protocols have been developed that relate to the maintenance of proper timing for these channels. For example, the SERDES Framer Interface Level 5 (hereinafter, “SFI-5”) protocol specification was developed to create a standard of maintaining the timing across output channels on electrical components, such as a demultiplexer. This protocol defines a deskew channel that is output from a demultiplexer and is used to align each of the channels at a subsequent component. The protocol also includes a notification function if the skew on one or more of the parallel channels exceeds a skew error margin. In such an instance, an alarm is generated and provided to a user.
In accordance with the SFI-5 protocol, this alarm only notifies a user that skew across the channels is too large, but does not specifically identify the channel(s) that have the skew problem. At initial configuration or testing of an integrated test, an alarm may be generated that notifies the user that the skew on the demultiplexer channels is outside an acceptable skew error margin. This alarm may also be generated if skew drifts outside of this skew error margin during operation. In all of these instances, the channel or channels responsible for this skew error is not identified.
This lack of specificity of SFI-5 skew error alarms present certain difficulties in correcting a demultiplexer having too much skew. Because the particular channel(s) responsible for the skew alarm are not identified, a user is unable to perform skew compensation without having additional information not provided in this alarm. Skew compensation could be performed on the channel responsible for generating the alarm in order to bring the skew of demultiplexer channels within an acceptable error margin. This compensation may include performing pre-skew or post-skew operations such that latency is added on one or more channels to improve the alignment of the channels.